Printing method, printing system, and print control apparatus

ABSTRACT

A printing method includes: (A) creating print data by rearranging an order in which a plurality of pieces of pixel data which make up image data are arranged; and (B) based on the print data, alternately repeating a dot-forming process for forming, on a medium, a row of dots along a movement direction by ejecting ink from a plurality of nozzles which move in the movement direction and a carrying process for carrying the medium in a carrying direction with respect to the nozzles, to form, on the medium, a plurality of the rows of dots arranged in the carrying direction. Every time the print data for performing a dot-forming process is to be created, positions, on the medium in the carrying direction, of the rows of dots to be formed by the nozzles during that dot-forming process are calculated and stored in a table, and the pixel data corresponding to the positions in the table are extracted from the image data, to create the print data.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority upon Japanese Patent ApplicationNo. 2005-084136 filed on Mar. 23, 2005, which is herein incorporated byreference.

BACKGROUND

1. Technical Field

The present invention relates to printing methods, printing systems, andprint control apparatuses.

2. Related Art

Inkjet printers which perform printing by ejecting ink onto media suchas paper (including cloth, overhead projector sheets, and so on) areknown. With such inkjet printers, an image made up of a plurality ofrows of dots is printed by repeating a dot-forming process for formingrows of dots by ejecting ink from a plurality of nozzles which move in amovement direction and a carrying process for carrying paper in acarrying direction. (See, for example, JP-A-11-268344.)

When ink is ejected from the nozzles, if a row of dots is formedoverlapping a position where a row of dots has already been formed, thatrow of dots will be formed darker compared to other rows of dots.Therefore, in a case where the position of a row of dots that can beformed during a certain dot-forming process is the same as the positionof a row of dots that can be formed during another dot-forming process,it is necessary not to form the row of dots in one of the dot-formingprocesses.

However, the amount of data needed to be stored would be too large ifprint data were created after performing this kind of comparing processfor all rows of dots.

SUMMARY

A primary aspect of the invention for resolving the above issues is aprinting method including:

creating print data by rearranging an order in which a plurality ofpieces of pixel data which make up image data are arranged; and

based on the print data, alternately repeating

-   -   a dot-forming process for forming, on a medium, a row of dots        along a movement direction by ejecting ink from a plurality of        nozzles which move in the movement direction and    -   a carrying process for carrying the medium in a carrying        direction with respect to the nozzles,        to form, on the medium, a plurality of the rows of dots arranged        in the carrying direction,

wherein, every time the print data for performing a dot-forming processis to be created,

positions, on the medium in the carrying direction, of the rows of dotsto be formed by the nozzles during that dot-forming process arecalculated and stored in a table, and

the pixel data corresponding to the positions in the table are extractedfrom the image data, to create the print data.

Other features of the present invention will become clear by reading thedescription of the present specification with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings wherein:

FIG. 1 is an explanatory diagram of an overall configuration of aprinting system;

FIG. 2 is an explanatory diagram of processes performed by a printerdriver;

FIG. 3 is a block diagram of an overall configuration of a printer;

FIG. 4A is a schematic diagram of an overall configuration of theprinter, and FIG. 4B is a transverse sectional view of an overallconfiguration of the printer;

FIG. 5 is a flowchart showing processes during printing;

FIG. 6 is an explanatory diagram showing an arrangement of nozzles;

FIG. 7A and FIG. 7B are explanatory diagrams of interlaced printing,wherein FIG. 7A shows the positions of a head and how dots are formed inpasses 1 to 5 and FIG. 7B shows the positions of the head and how dotsare formed in passes 1 to 6;

FIG. 8 is an explanatory diagram of upper-end printing and lower-endprinting;

FIG. 9A is an explanatory diagram of virtual printing, and FIG. 9B is anexplanatory diagram of parameters for setting conditions for virtualprinting;

FIG. 10 is a flowchart showing creation of a scheduling table in a firstreference example;

FIG. 11A is an explanatory diagram of the scheduling table up until afirst pass in “virtual printing 1”, FIG. 11B is an explanatory diagramof the scheduling table up until a second pass in “virtual printing 1”,FIG. 11C is an explanatory diagram of the scheduling table whenperforming the process in S109 for the first time with P=2, FIG. 11D isan explanatory diagram of the scheduling table up until the passesperformed for the second time in “virtual printing 2”, and FIG. 11E isan explanatory diagram of the scheduling table up until the passesperformed for the third time in “virtual printing 2”;

FIG. 12 is an explanatory diagram showing how to use the schedulingtable in a first reference example;

FIG. 13 is an explanatory diagram of parameters for setting conditionsfor virtual printing in a first embodiment;

FIG. 14 is a flowchart showing a process for creating the schedulingtable for pass m in upper-end printing according to the firstembodiment;

FIG. 15A through FIG. 15E are explanatory diagrams of stages in theprocess for creating the scheduling table for pass 1;

FIG. 16 is a flowchart showing a process for creating the schedulingtable for pass m in normal printing according to the first embodiment;

FIG. 17A through FIG. 17C show, at the bottom thereof, scheduling tablesfor each of passes 4 through 6 and show, at the top thereof, conceptualdiagrams of the content of processes when creating the schedulingtables;

FIG. 18 is a flowchart showing a process for creating the schedulingtable for lower-end printing according to the first embodiment;

FIG. 19 is a flowchart showing a process for creating a dummy schedulingtable;

FIG. 20A through FIG. 20C are conceptual diagrams for explaining thedummy scheduling table;

FIG. 21 is a flowchart showing a process for creating scheduling tablesfor each pass based on the dummy scheduling table;

FIG. 22A through FIG. 22C are conceptual diagrams for explaining thescheduling tables for each pass;

FIG. 23A is an explanatory diagram showing image data (image data afterhalftoning) before rasterization, and FIG. 23B is an explanatory diagramshowing the order of pixel data before rasterization;

FIG. 24A is an explanatory diagram showing a rasterizing process forcreating print data for pass 1, and FIG. 24B is an explanatory diagramshowing the order of pixel data after rasterization, the order of pixeldata being contained in the print data for pass 1;

FIG. 25 is an explanatory diagram of a dot-forming process based on theprint data;

FIG. 26A and FIG. 26B are explanatory diagrams of partial overlappedprinting;

FIG. 27 is an explanatory diagram of upper-end printing and lower-endprinting in partial overlapped printing;

FIG. 28 is an explanatory diagram of parameters for setting conditionsfor virtual printing in a second embodiment;

FIG. 29 is a flowchart showing a process for creating a scheduling tablefor pass m in upper-end printing according to the second embodiment;

FIG. 30A through FIG. 30C are explanatory diagrams of stages in theprocess for creating the scheduling table for pass 1;

FIG. 31 is a flowchart showing a process for creating the schedulingtable for pass m in normal printing according to the second embodiment;

FIG. 32A through FIG. 32C are explanatory diagrams of stages in theprocess for creating the scheduling table for pass 4;

FIG. 33 is a flowchart showing a process for creating the schedulingtable for each pass during lower-end printing according to the secondembodiment;

FIG. 34A through FIG. 34D are explanatory diagrams of stages in theprocess for creating the scheduling table for pass 10;

FIG. 35A is an explanatory diagram showing a rasterizing process forcreating print data for pass 4, and FIG. 35B is an explanatory diagramshowing the order of pixel data after rasterization, the order of pixeldata being contained in the print data for pass 4; and

FIG. 36 is a conceptual diagram of a process up until pass 4 isperformed.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

At least the following matters will be made clear by the explanation inthe present specification and the description of the accompanyingdrawings.

A printing method includes:

creating print data by rearranging an order in which a plurality ofpieces of pixel data which make up image data are arranged; and

based on the print data, alternately repeating

-   -   a dot-forming process for forming, on a medium, a row of dots        along a movement direction by ejecting ink from a plurality of        nozzles which move in the movement direction and    -   a carrying process for carrying the medium in a carrying        direction with respect to the nozzles,        to form, on the medium, a plurality of the rows of dots arranged        in the carrying direction,

wherein, every time the print data for performing a dot-forming processis to be created,

positions, on the medium in the carrying direction, of the rows of dotsto be formed by the nozzles during that dot-forming process arecalculated and stored in a table, and

the pixel data corresponding to the positions in the table are extractedfrom the image data, to create the print data.

With this kind of printing method, the amount of data which needs to bestored can be reduced, since a table can be created for each dot-formingprocess.

In this printing method, it is preferable that print data for performinga dot-forming process which is to be performed after a certaindot-forming process is created while the certain dot-forming process isperformed based on the print data. With this, the time until completionof printing is kept short.

In this printing method, it is preferable that, when creating print datafor performing a certain dot-forming process, a comparing process isperformed in which positions, on the medium in the carrying direction,of the rows of dots to be formed by the nozzles during an otherdot-forming process are compared with the positions stored in the table,and if there is any matching position as a result of the comparison,that position is deleted from the table, and the pixel datacorresponding to the positions in the table after the comparing processare extracted from the image data, to create the print data. In thisway, dot rows are prevented from being formed in an overlapped manner.Further, it is preferable that the certain dot-forming process is adot-forming process for performing upper-end printing for forming therows of dots in an upper-end portion of the medium, and the otherdot-forming process is a dot-forming process for performing normalprinting for forming the rows of dots in a central portion of themedium. This allows to improve the quality of a printed image.

In this printing method, it is preferable that, in a case where, duringthe above-mentioned dot-forming process, a certain nozzle forms dots atspecific positions in the movement direction and, during a differentdot-forming process performed after the above-mentioned dot-formingprocess, an other nozzle forms dots such as to fill in spaces betweenthe dots formed at the specific positions, information regarding thespecific positions in the movement direction is associated with aposition, on the medium in the carrying direction, of the row of dots tobe formed by the certain nozzle and the information is stored in thetable in association therewith. Further, it is preferable that the othernozzle is positioned at an end in the carrying direction of theplurality of nozzles. This is because nozzles positioned at end portionstend to eject ink defectively.

In this printing method, it is preferable that a computer having aprinter driver installed thereon creates the print data. Note, however,that the print control apparatus and the printing apparatus may beprovided as a single unit.

Further, a printing system includes:

a print control apparatus for creating print data by rearranging anorder in which a plurality of pieces of pixel data which make up imagedata are arranged; and

a printing apparatus that alternately repeats, based on the print data,

-   -   a dot-forming process for forming, on a medium, a row of dots        along a movement direction by ejecting ink from a plurality of        nozzles which move in the movement direction and    -   a carrying process for carrying the medium in a carrying        direction with respect to the nozzles,        to form, on the medium, a plurality of the rows of dots arranged        in the carrying direction,

wherein, every time the print data for performing a dot-forming processis to be created,

the print control apparatus

-   -   calculates and stores, in a table, positions, on the medium in        the carrying direction, of the rows of dots to be formed by the        nozzles during that dot-forming process, and    -   extracts, from the image data, the pixel data corresponding to        the positions in the table, to create the print data.

With this kind of printing system, the amount of data which needs to bestored can be reduced, since a table can be created for each dot-formingprocess.

Further, provided is a print control apparatus provided with a driverfor controlling a printing apparatus, the driver including:

a code for creating print data by rearranging an order in which aplurality of pieces of pixel data which make up image data are arranged;

a code for causing the printing apparatus to alternately repeat, basedon the print data,

-   -   a dot-forming process for forming, on a medium, a row of dots        along a movement direction by ejecting ink from a plurality of        nozzles which move in the movement direction and    -   a carrying process for carrying the medium in a carrying        direction with respect to the nozzles,        to cause the printing apparatus to form, on the medium, a        plurality of the rows of dots arranged in the carrying        direction; and

a code, utilized every time the print data for performing a dot-formingprocess is to be created, for

-   -   calculating and storing, in a table, positions, on the medium in        the carrying direction, of the rows of dots to be formed by the        nozzles during that dot-forming process, and    -   extracting, from the image data, the pixel data corresponding to        the positions in the table, to create the print data.

With this kind of print control apparatus, the amount of data whichneeds to be stored can be reduced, since a table can be created for eachdot-forming process.

===Configuration of Printing System===

An embodiment of a printing system (computer system) is described belowwith reference to the drawings. However, the description of thefollowing embodiment also includes implementations relating to acomputer program and a storage medium which stores the computer program,for example.

FIG. 1 is an explanatory diagram showing an external structure of aprinting system. A printing system 100 is provided with a printer 1, acomputer 110, a display device 120, an input device 130, and arecord/play device 140. The printer 1 is a printing apparatus forprinting images on a medium such as paper, cloth, or film. The computer110 is communicably connected to the printer 1, and outputs print datacorresponding to an image to be printed to the printer 1 in order toprint the image with the printer 1. The display device 120 has adisplay, and displays user interfaces of programs such as an applicationprogram or a printer driver. The input device 130, which is for examplea keyboard 130A and a mouse 130B, is used to input operations for theapplication program, settings of the printer driver, and the like. Aflexible disk drive device 140A and/or a CD-ROM drive device 140B areemployed as the record/play device 140.

A printer driver is installed on the computer 110. The printer driver isa program for making the display device 120 achieve functionality ofdisplaying the user interface, and also for making the computer 110achieve functionality of converting image data that has been output fromthe application program into print data. The printer driver is stored ona storage medium (a computer-readable storage medium) such as a flexibledisk FD or a CD-ROM. Also, the printer driver can be downloaded onto thecomputer 110 via the Internet. It should be noted that this program ismade up of codes for achieving the various functions.

Note also that “printing apparatus” means an apparatus for printingimages on a medium, and, for example, the printer 1 can be taken as anexample thereof. Furthermore, “print control apparatus” means anapparatus for controlling the printing apparatus, and, for example, acomputer on which the printer driver is installed can be taken as anexample thereof. Further, “printing system” means a system whichcontains at least the printing apparatus and the print controlapparatus.

===Printer Driver===

<Regarding the Printer Driver>

FIG. 2 is a schematic explanatory diagram of basic processes carried outby the printer driver. Components that have already been described areassigned-identical reference numerals and thus further descriptionthereof is omitted.

On the computer 110, computer programs such as a video driver 112, anapplication program 114, and a printer driver 116 operate under anoperating system installed on the computer. The video driver 112 has afunction of displaying, for example, the user interface on the displaydevice 120 in accordance with display commands from the applicationprogram 114 and/or the printer driver 116. The application program 114has, for example, functions which enable image editing and creates datarelated to images (image data). A user can give an instruction to printan image edited in the application program 114 via the user interface ofthe application program 114. Upon receiving the print instruction, theapplication program 114 outputs the image data to the printer driver116.

The printer driver 116 receives the image data from the applicationprogram 114, converts the image data to print data, and outputs theprint data to the printer. Here, “print data” refers to data in a formatwhich can be interpreted by the printer 1 and which includes a varietyof command data and pixel data. Here, “command data” refers to data forinstructing the printer to carry out specific operations. Furthermore,“pixel data” refers to data related to pixels that make up an image tobe printed (a print image), and is, for example, data about a dot to beformed in a certain position on the paper corresponding to a certainpixel (data about dot color and size, for example).

In order to convert the image data that is output from the applicationprogram 114 to print data, the printer driver 116 carries out processessuch as resolution conversion, color conversion, halftoning, andrasterization. The following is a description of processes carried outby the printer driver 116.

Resolution conversion is a process in which image data (i.e., text data,image data, etc.) output from the application program 114 is convertedto a resolution for printing on paper. For example, when the resolutionfor printing an image on paper is specified as 720×720 dpi, then theimage data received from the application program 114 is converted toimage data with a resolution of 720×720 dpi. It should be noted that,after resolution conversion, the image data is multi-gradation RGB data(e.g., with 256 gradations) that is expressed using an RGB color space.Hereinafter, RGB data obtained by subjecting image data to resolutionconversion is referred to as “RGB image data.”

Color conversion is a process in which RGB data is converted to CMYKdata that is expressed using a CMYK color space. It should be noted thatCMYK data is data that corresponds to the colors of the ink of theprinter. The color conversion processing is carried out by the printerdriver 116 referencing a table (a color conversion look-up table LUT) inwhich gradation values of RGB image data are associated with gradationvalues of CMYK image data. Through this color conversion, RGB data ofthe pixels is converted to CMYK data that corresponds to ink colors. Itshould be noted that, after color conversion, the data is 256-gradationCMYK data expressed with a CMYK color space. Hereinafter, CMYK dataobtained by subjecting RGB image data to color conversion is referred toas “CMYK image data.”

Halftoning is a process through which data with a high number ofgradations is converted to data of a number of gradations that can beformed by the printer. For example, through halftoning, data expressing256 gradations is converted to 1-bit data expressing two gradations or2-bit data expressing four gradations. Through halftoning, pixel data iscreated using dithering, gamma correction, error diffusion, and thelike, such that the printer can form dots in a dispersed manner. Duringhalftoning, the printer driver 116 references a dither table whenperforming dithering, a gamma table when performing gamma correction,and an error memory for storing diffused errors when performing errordiffusion. Halftoned data has a resolution (for example, 720×720 dpi)identical to the above-mentioned RGB data. In this example, halftoneddata is made up of 2 bits of data per pixel.

Rasterization is a process whereby image data which is made up of pixeldata arranged in a matrix is rearranged into an order of data fortransfer to the printer. Rasterized data is output to the printer aspixel data contained in print data. This rasterization process isperformed by the printer driver 116 referencing the scheduling table.The scheduling table will be described further below.

===Configuration of the Printer===

<Regarding a Configuration of the Inkjet Printer>

FIG. 3 is a block diagram of an overall configuration of the printer 1of the present embodiment. FIG. 4A is a schematic diagram of an overallconfiguration of the printer 1 of the present embodiment. FIG. 4B istransverse sectional view of an overall configuration of the printer 1of the present embodiment. A basic configuration of the printeraccording to the present embodiment is described below.

The printer 1 according to the present embodiment includes a carryingunit 20, a carriage unit 30, a head unit 40, a detector group 50, and acontroller 60. Having received print data from the computer 110, whichis an external device, the printer 1 controls the various units (thecarrying unit 20, the carriage unit 30, and the head unit 40) using thecontroller 60. The controller 60 controls the units in accordance withthe print data that is received from the computer 110 to print an imageon paper. The detector group 50 monitors the conditions within theprinter 1, and outputs the results of this detection to the controller60. The controller 60 controls each unit based on the detection resultsoutput by the detector group 50.

The carrying unit 20 is for feeding a medium (for example, paper S,etc.) into a printable position and carrying the paper in apredetermined direction (hereafter called a carrying direction) by apredetermined carry amount during printing. In other words, the carryingunit 20 functions as a carrying mechanism (a carrying means) forcarrying paper. The carrying unit 20 is provided with a paper-supplyingroller 21, a carrying motor 22 (hereafter also called a PF motor), acarrying roller 23, a platen 24, and a paper-discharge roller 25. Note,however, that the carrying unit 20 does not necessarily have to includeall of these components in order to function as a carrying mechanism.The paper-supplying roller 21 is a roller for supplying, into theprinter, paper that has been inserted into a paper insert opening. Thepaper-supplying roller 21 has a cross-sectional shape in the shape ofthe letter D, and the length of its circumference portion is set longerthan the carrying distance to the carrying roller 23, so that the papercan be carried up to the carrying roller 23 using this circumferenceportion. The carrying motor 22 is a motor for carrying paper in thecarrying direction, and is constituted by a DC motor, for example. Thecarrying roller 23 is a roller for carrying the paper S, which has beenfed by the paper-supplying roller 21, up to a printable region, and isdriven by the carrying motor 22. The platen 24 supports the paper S onwhich printing is being performed. The paper-discharge roller 25 is aroller for discharging the paper S to the outside, and is provideddownstream in the carrying direction with respect to the printableregion. The paper-discharge roller 25 rotates in synchronization withthe carrying roller 23.

The carriage unit 30 is for causing the head to move (also referred toas “scan”) in a predetermined direction (hereafter referred to as the“movement direction”). The carriage unit 30 has a carriage 31 and acarriage motor 32 (also called a “CR motor”). The carriage 31 can bemoved back and forth in the movement direction. (The head is thus movedin the movement direction.) Furthermore, the carriage 31 detachablyretains an ink cartridge containing ink. The carriage motor 32 is amotor for moving the carriage 31 in the movement direction, and isconstituted by a DC motor, for example.

The head unit 40 is for ejecting ink onto paper. The head unit 40 has ahead 41. The head 41 has a plurality of nozzles and ejects inkintermittently from each of the nozzles. The head 41 is provided to thecarriage 31. Therefore, when the carriage 31 moves in the movementdirection, the head 41 also moves in the movement direction. Dot lines(raster lines) are formed on the paper in the movement direction as aresult of the head 41 intermittently ejecting ink while moving in themovement direction.

The detector group 50 includes a linear encoder 51, a rotary encoder 52,a paper detection sensor 53, an optical sensor 54, and so on. The linearencoder 51 is for detecting the position of the carriage 31 in themovement direction. The rotary encoder 52 is for detecting the amount ofrotation of the carrying roller 23. The paper detection sensor 53 is fordetecting the position of the front end of the paper to be printed. Thepaper detection sensor 53 is provided in a position where it can detectthe position of the front end of the paper as the paper is being fedtoward the carrying roller 23 by the paper-supplying roller 21. Itshould be noted that the paper detection sensor 53 is a mechanicalsensor that detects the front end of the paper through a mechanicalmechanism. More specifically, the paper detection sensor 53 has a leverthat can be rotated in the carrying direction, and this lever isdisposed such that it protrudes into the path over which the paper iscarried. In this way, the front end of the paper comes into contact withthe lever and the lever is rotated, and thus the paper detection sensor53 detects the position of the front end of the paper by detecting themovement of the lever. The optical sensor 54 is attached to the carriage31. The optical sensor 54 detects whether or not the paper is present byits light-receiving section detecting reflected light of the light thathas been irradiated onto the paper from a light-emitting section. Theoptical sensor 54 detects the positions of the edges of the paper whilebeing moved by the carriage 31, and in this way it can detect the widthof the paper. The optical sensor 54 can also detect the front end (thedownstream end in the carrying direction; also referred to as the upperend) and the bottom end (the upstream end in the carrying direction;also referred to as the lower end) of the paper according to thecircumstances. The optical sensor 54 detects the ends of the paperoptically, and thus has higher detection accuracy than the mechanicalpaper detection sensor 53.

The controller 60 is a control unit (controlling means) for carrying outcontrol of the printer. The controller 60 has an interface section 61, aCPU 62, a memory 63, and a unit control circuit 64. The interfacesection 61 serves to exchange data between the computer 110, which is anexternal device, and the printer 1. The CPU 62 is a computationalprocessing device for carrying out overall control of the printer. Thememory 63 is for reserving a work area and an area for storing theprograms for the CPU 62, for instance, and includes storing means suchas a RAM or an EEPROM. The CPU 62 controls the various units via theunit control circuit 64 in accordance with programs stored in the memory63.

<Regarding the Printing Operation>

FIG. 5 is a flowchart of processes during printing. The processesdescribed below are executed by the controller 60 controlling thevarious units in accordance with a program stored in the memory 63. Thisprogram includes codes for executing the various processes.

Receive Print Command (S001): First, the controller 60 receives a printcommand from the computer 110 via the interface section 61. This printcommand is included in the header of the print data transmitted from thecomputer 110. The controller 60 then analyzes the content of the variouscommands included in the print data that is received and uses the unitsto perform the following paper supplying process, carrying process,dot-forming process, and so on.

Paper Supplying Process (S002): The paper supplying process is a processfor supplying paper to be printed into the printer and positioning thepaper at a print start position (also referred to as the “indexedposition”). The controller 60 rotates the paper-supplying roller 21 tofeed the paper to be printed up to the carrying roller 23. Next, thecontroller 60 rotates the carrying roller 23 to position the paper,which has been fed from the paper-supplying roller 21, at the printstart position. When the paper is positioned at the print startposition, at least some of the nozzles of the head 41 are in oppositionto the paper.

Dot-Forming Process (S003): The dot-forming process is a process forintermittently ejecting ink from the head that moves in the movementdirection so as to form dots on the paper. The controller 60 drives thecarriage motor. 32 to move the carriage 31 in the movement direction.The controller 60 then causes the head to eject ink in accordance withthe print data while the carriage 31 is moving. Dots are formed on thepaper when ink droplets ejected from the head land on the paper. Sinceink is intermittently ejected from the moving head, rows of dots (rasterlines) made up of a plurality of dots arranged in the movement directionare formed on the paper.

Carrying Process (S004): The carrying process is a process for movingthe paper relative to the head in the carrying direction. The controller60 drives the carrying motor to rotate the carrying roller and therebycarry the paper in the carrying direction. Through this carryingprocess, the head 41 can form dots at positions that are different fromthe positions of the dots formed in the preceding dot-forming process.

Paper Discharge Determination (S005): The controller 60 determineswhether or not to discharge the paper being printed. The paper is notdischarged if there still is data to be printed on the paper beingprinted. The controller 60 alternately repeats the dot-forming processand the carrying process until there is no longer data to be printed,thereby gradually printing an image made of dots on the paper.

Paper Discharge Process (S006): When there is no longer data to beprinted on the paper being printed, the controller 60 discharges thepaper by rotating the paper-discharge roller. It should be noted thatwhether or not to discharge the paper can also be determined based on apaper discharge command included in the print data.

Printing Over Determination (S007): Next, the controller 60 determineswhether or not to continue printing. If the next sheet of paper is to beprinted, then printing is continued and the paper supplying process forthe next sheet of paper is started. If the next sheet of paper is not tobe printed, then the printing operation is ended.

<Regarding the Nozzles>

FIG. 6 is an explanatory diagram showing the arrangement of the nozzlesin a lower face of the head 41. A black ink nozzle group K, a cyan inknozzle group C, a magenta ink nozzle group M, and a yellow ink nozzlegroup Y are formed in the lower face of the head 41. Each nozzle groupis provided with a plurality of nozzles (in this embodiment, 180nozzles), which are ejection openings for ejecting inks of therespective colors.

The plurality of nozzles in each nozzle group are arranged in a row at aconstant spacing (nozzle pitch: k·D) in the carrying direction. Here, Dis the minimum dot pitch in the carrying direction (that is, theinterval between dots formed on the paper S at the maximum resolution).Further, k is an integer of 1 or more. For example, if the nozzle pitchis 180 dpi ( 1/180 inch) and the dot pitch in the carrying direction is540 dpi ( 1/540 inch), then k=3.

Each nozzle in the nozzle groups is assigned a number (#1 to #180) thatbecomes smaller the further downstream the nozzle is located. That is, anozzle #1 is positioned more downstream in the carrying direction than anozzle #180. Note also that the optical sensor 54 is provided insubstantially the same position as the nozzle #180, which is on thefurthest upstream side, with respect to its position in the papercarrying direction.

Each nozzle is provided with an ink chamber (not shown) and a piezoelement. Driving the piezo element causes the ink chamber to contractand expand, thereby ejecting an ink droplet from the nozzle.

Printing Method of a First Embodiment

<Interlaced Printing (Normal Printing)>

FIG. 7A and FIG. 7B are explanatory diagrams of interlaced printing.FIG. 7A shows the positions of the head (or nozzle group) and how dotsare formed in passes 1 to 5. FIG. 7B shows the positions of the head andhow dots are formed in passes 1 to 6.

To simplify the description, only one nozzle group of the plurality ofnozzle groups is shown, and the number of nozzles in the nozzle group isreduced (to six nozzles in this case). In this diagram, nozzlesindicated by black circles are nozzles allowed to eject ink, whereasnozzles indicated by white circles are nozzles not allowed to eject ink.It should be noted that, for convenience's sake, the head (and thenozzle group) is illustrated as if it is moving with respect to thepaper, but the diagrams show the relative positional relationship of thehead and the paper, and in fact it is the paper that is moving in thecarrying direction. For the sake of description, each nozzle is shown asif it only forms a few dots (the circles in the drawings), but inactuality many dots are lined up in the movement direction because inkdroplets are ejected intermittently from each nozzle moving in themovement direction. These rows of dots are also called “raster lines.”Dots indicated by black circles are dots which are formed in the lastpass, while dots which are indicated by white circles are dots formed inprevious passes. Note that a “pass” is the process for forming dots byejecting ink from moving nozzles (i.e., a dot-forming process). Eachpass is performed in alternation with a process for carrying the paperin the carrying direction (i.e., a carrying process).

“Interlaced printing” refers to a printing method in which k is at least2 and at least one raster line that is not recorded exists between theraster lines that are recorded in a single pass. For example, in theprinting method shown in FIG. 7A and FIG. 7B, two raster lines existbetween the raster lines formed in one pass.

With interlaced printing, every time the paper is carried in thecarrying direction by a constant carry amount F, each nozzle records araster line immediately above the raster line that was recorded in theimmediately prior pass. The conditions for performing recording in thismanner with a fixed carry amount are: (1) that the number of nozzles N(an integer) which are allowed to eject ink is coprime with k, and (2)that the carry amount F is set to N·D.

In the figure, the nozzle row has six nozzles arranged in the carryingdirection. Since the nozzle pitch k of the nozzle row is three, onlyfive nozzles (nozzle #1 through nozzle #5), and not all the nozzles, areused, in order to satisfy the interlaced printing condition that “N andk must be coprime.” Furthermore, because five nozzles are used, thepaper is carried using a carry amount of 5·D. As a result, using anozzle row with a nozzle pitch of 180 dpi (3·D), for example, dots areformed on the paper with a dot spacing of 540 dpi (=D). (It should benoted that the number of nozzles in actuality is greater than six, sothe number of nozzles N that are allowed to eject ink is greater, as isthe carry amount F.) The figures show a first raster line being formedby nozzle #1 in pass 1, a second raster line being formed by nozzle #2in pass 1, a third raster line being formed by nozzle #1 in pass 2, anda fourth raster line being formed by nozzle #3 in pass 1. From the fifthraster line and on, raster lines are formed continuously in the carryingdirection.

<Upper-End Printing and Lower-End Printing>

When interlaced printing is performed from the start as described above,some raster lines may, in some cases, not be formed continuously. Forexample, in FIG. 7A and FIG. 7B, the first, second, third, and fourthraster lines downstream in the carrying direction are not formed asraster lines which are continuous in the carrying direction.Accordingly, the printer forms raster lines continuous in the carryingdirection by performing “upper-end printing,” which is described below.

When interlaced printing is finished at the end, some raster lines maynot be formed continuously. For example, in FIG. 7A and FIG. 7B, rasterlines on the upstream side in the carrying direction are not formed asraster lines which are continuous in the carrying direction.Accordingly, the printer forms raster lines continuous in the carryingdirection by performing “lower-end printing,” which is described below,after performing interlaced printing.

FIG. 8 is an explanatory diagram of upper-end printing and lower-endprinting.

In FIG. 8, pass 1 through pass 3 correspond to upper-end printing, pass4 through pass 9 correspond to normal printing (interlaced printing),and pass 10 through pass 12 correspond to lower-end printing. Inupper-end printing, the carry amount during the carrying process betweenpass 1 and pass 2 and the carry amount during the carrying processbetween pass 2 and pass 3 are D. In lower-end printing, the carry amountduring the carrying process between pass 10 and pass 11 and the carryamount during the carrying process between pass 11 and pass 12 are D.

By performing upper-end printing, it is possible to form raster lineswhich are continuous in the carrying direction from the first rasterline. Further, by performing lower-end printing, it is possible to formraster lines which are continuous in the carrying direction up to thelast raster line.

Note that the “upper-end printing region” in the drawing indicates theregion from the raster line furthest downstream in the carryingdirection to the raster line furthest upstream in the carrying directionof the raster lines formed by upper-end printing. The upper-end printingregion here is the region from the first raster line to the fifteenthraster line. Furthermore, note that the “lower-end printing region” inthe drawing indicates the region from the raster line furthestdownstream in the carrying direction of the raster lines formed bylower-end printing to the raster line furthest upstream in the carryingdirection. The lower-end printing region here is the region from thethirty-eighth raster line to the fifty-second raster line. The “normalprinting region” in the drawing indicates the region between theupper-end printing region and the lower-end printing region. The normalprinting region here is the region from the sixteenth raster line to thethirty-seventh raster line. All the raster lines in the normal printingregion are formed through normal printing (normal interlaced printing).On the other hand, the upper-end printing region contains not onlyraster lines formed through upper-end printing, but also raster linesformed through normal printing. The lower-end printing region, too,contains not only raster lines formed through lower-end printing, butalso raster lines formed through normal printing.

<Regarding Unused Nozzles>

Incidentally, despite the fact that the nozzle #1 through the nozzle #5can eject ink in normal printing, the nozzle #5 is not allowed to ejectink during pass 1 in upper-end printing. If the thirteenth raster linewere formed by ejecting ink from the nozzle #5 during pass 1, then thenozzle #1 would form the same raster line during pass 5, meaning thatthe thirteenth raster line would be formed overlapped and thereforebecome darker compared to other raster lines. It is possible to set thenozzle #1 during pass 5 as the unused nozzle, but in the presentembodiment, the nozzle #1 during pass 5, in which normal interlacedprinting is performed, is given priority, and the nozzle #5 during pass1 is set as the unused nozzle. By giving priority to a nozzle during apass when normal interlaced printing is performed, and not to a nozzleduring a pass when upper-end printing is performed, the image quality ofthe print image improves, because there are more raster lines formedthrough normal interlaced printing.

Similarly, the nozzle #3 through the nozzle #5 during pass 2 are in aposition at which the eighth, eleventh, and fourteenth raster lines canbe formed, but they do not eject ink, because the same raster lines willbe formed by the nozzle #1 through the nozzle #3 during pass 4. The sameapplies to lower-end printing, in which the nozzle #1 through the nozzle#3 during pass 11 and the nozzle #1 during pass 12 do not eject ink.

As described above, nozzles which should not eject ink appear whenperforming upper-end printing and lower-end printing. It is thereforenecessary for the printer driver to select the unused nozzles.

FIRST REFERENCE EXAMPLE

With the printing method of the first reference example, the printerdriver first creates a scheduling table. The scheduling table is a tablein which the positions of raster lines are associated with nozzlesforming those raster lines. Based on the scheduling table, the printerdriver performs rasterization and also determines which nozzles are toeject ink (and which nozzles are unused).

The printing method of the first reference example is described in orderbelow. Note, however, that upper-end printing is described and adescription of lower-end printing is omitted, in order to simplify thedescription.

<Regarding Creation of the Scheduling Table>

According to the first reference example, when creating the schedulingtable, the printer driver virtually moves the head (a virtual head) withrespect to the paper, just like during actual printing. The printerdriver creates the scheduling table by associating the positions of thenozzles on the head with the positions of the raster lines.

FIG. 9A is an explanatory diagram of virtual printing. FIG. 9B is anexplanatory diagram of parameters for setting conditions for virtualprinting. The parameters for this virtual printing are determined basedon the printing mode and the paper size.

During “virtual printing 1”, as in the actual upper-end printing, thehead is virtually moved with respect to the paper. In other words, thenozzle pitch k of the head performing upper-end printing is 3. The carryamount F of the carrying process between pass 1 and pass 2 during“virtual printing 1” is 1·D. The first nozzle in the virtual head is #1,and the last nozzle is #5. Note that the printer driver does not takeinto consideration the presence of unused nozzles. A position Ls of thefirst nozzle (the nozzle #1) during the first pass (pass 1) during“virtual printing 1” is the same as the position in the carryingdirection of the first raster line. A position Lf of the first nozzle(the nozzle #1) during the last pass (pass 2) during “virtual printing1” is the same as the position in the carrying direction of the secondraster line.

During “virtual printing 2”, as in the actual interlaced printing, thehead is virtually moved with respect to the paper. Unlike “virtualprinting 1” described above, the carry amount F is 5·D. Further, aposition Ls of the first nozzle (the nozzle #1) during the first pass(pass 3) in “virtual printing 2” is the same as the position in thecarrying direction of the third raster line, and a position Lf of thefirst nozzle (the nozzle #1) during the last pass (pass 6) in “virtualprinting 2” is the same as the position in the carrying direction of theeighteenth raster line.

FIG. 10 is a flowchart showing creation of a scheduling table in thefirst reference example. FIG. 11A through FIG. 11E are explanatorydiagrams of the scheduling table in the first reference example. Thescheduling table is recorded in the memory on the computer. The printerdriver executes a scheduling table creating process using the parametersfor the virtual printing described above.

The printer driver first initializes a virtual printing number P (S101).The printer driver thereby reads from the memory the parameters whichare set as the conditions of “virtual printing 1”.

Next, the printer driver sets the position of a starting nozzle based onthe parameters which have been read (S102). In the first referenceexample, the position of the nozzle #1 is set to “1” (specifically, theposition of the first raster line in the carrying direction).

Next, the printer driver initializes a nozzle number i, and sets i=1(S103).

Next, the printer driver calculates a position L of the nozzle #1(S104). The position of the nozzle #1 is calculated from the nozzlepitch k, the carry amount F, the nozzle number i, the starting positionLs, and so on. At first, the position of the nozzle #1 is set to “1,”which is the same as the starting position Ls.

Next, the printer driver determines whether or not the position “1” isalready registered in the scheduling table (S105).

At first, nothing is registered in the scheduling table, so thedetermination is “No.”

Next, the printer driver associates the position “1” with the nozzle #1and registers this to the scheduling table (S106).

The printer driver determines whether or not the nozzle #i is the lastnozzle (S107). The information on the last nozzle is set in theparameters of the virtual printing described above. Here, the nozzle #1is not the last nozzle, so this determination is “No.”

The printer driver increments the nozzle number i in order to performthe process for the next nozzle (S108). Here, the nozzle number isincremented from 1 to 2.

The printer driver repeats the processes in S104 through S107 above andcreates the scheduling table in which the position L and the nozzlenumber are associated for the nozzle #2 through the nozzle #5.

FIG. 11A is an explanatory diagram of the scheduling table created bythe printer driver up until this point. At this point, each nozzle isassociated with the position of each nozzle for the virtual pass 1 inthe scheduling table.

The processes in S104 through S107 are repeated until the last nozzle isreached (the nozzle #5), and when the answer is “Yes” for S107, theprinter driver determines whether or not the first nozzle (#1) hasreached the finishing position Lf. At first, the position of the nozzle#1 is set to “1,” which is the same as the starting position Ls, so theanswer is “No.”

Next, the printer driver sets the position of the first nozzle to aposition equal to the current position plus the carry amount F. By doingthis, the position of the head moves by the carry amount F virtuallywith respect to the paper. At first, through this process, the positionof the first nozzle moves from a position “1” to a position “2.” Thecreation of the scheduling table for the virtual pass 1 is therebyfinished, and the creation of the scheduling table for the virtual pass2 begins.

The printer driver initializes the nozzle number i (S103), repeats theprocesses in S104 through S107 above, and creates the scheduling tablein which the position L and the nozzle number are associated for thenozzle #1 through the nozzle #5.

FIG. 11B is an explanatory diagram of the scheduling table created bythe printer driver up until this point. At this point, each nozzle isassociated with the position of each nozzle for the virtual pass 1 andthe virtual pass 2 in the scheduling table.

After the creation of the scheduling table for the virtual pass 2 isfinished, the printer driver determines whether or not the first nozzle(#1) has reached the finishing position Lf. At this point, the nozzle#1, which is the first nozzle, has reached the finishing position “2,”so the answer is “Yes.”

The printer driver increments the virtual printing number P in order toperform the processes for the next virtual printing (S112). Here, thevirtual printing number is incremented from 1 to 2. The printer driverthen reads from the memory the parameters set as conditions for “virtualprinting 2”, and, as in the case of “virtual printing 1” describedabove, registers the relationships between the nozzle positions and thenozzle numbers in the scheduling table. FIG. 11C is an explanatorydiagram of the scheduling table when the positions L and nozzle numbersare associated and registered, for the nozzles #1 through #5 for a firstpass of “virtual printing 2”. (In other words, FIG. 11C is anexplanatory diagram of the scheduling table when performing S109 for thefirst time when P=2.)

When the head position is virtually moved once by the carry amount Fduring “virtual printing 2”, the position of the nozzle #1 becomes “8”(S104).

Note, however, that information associating the position 8 and thenozzle number 3 has already been stored in the scheduling table. Theprinter driver therefore answers “Yes” in S105. The printer driver thenoverwrites the nozzle number 3 which corresponds to the position 8 andregisters the nozzle number 1 in the scheduling table. In other words,by performing this overwriting, the information associating the position8 with the nozzle number 3 (see FIG. 11B) which was registered duringthe processes for “virtual printing 1” is deleted from the schedulingtable, and in its place, information associating the position 8 with thenozzle number 1 is registered in the scheduling table.

Similarly, information associating the position 11 with the nozzlenumber 4 has already been stored in the scheduling table during theprocesses for “virtual printing 1”. This information is overwritten withinformation associating the position 11 with the nozzle number 2 in theprocesses for “virtual printing 2”. Furthermore, information associatingthe position 14 with the nozzle number 5 has already been stored in thescheduling table during the processes for “virtual printing 1”. Thisinformation is overwritten with information associating the position 14with the nozzle number 3 in the processes for “virtual printing 2”.

A position 17 of the nozzle #4 has not yet been registered at this time.Similarly, a position 20 of the nozzle #5 has not yet been registered atthis time. The answer at S105 is therefore “No,” and informationassociating these positions and nozzles is added to the schedulingtable.

FIG. 11D is an explanatory diagram of the scheduling table when thepositions L and the nozzle numbers are associated and registered for thenozzle #1 through the nozzle #5 for the second pass of “virtual printing2”. In FIG. 11D, the information in bold outline is information whichhas been registered by overwriting.

Next, the printer driver sets the position of the first nozzle to aposition equal to the current position plus the carry amount F, andperforms processes for the third pass of “virtual printing 2”. At thispoint, the position of the nozzle #1 is 13. Information associating theposition 13 and the nozzle number 5 has already been stored in thescheduling table. The printer driver therefore overwrites the nozzlenumber 1 and registers the nozzle number 5 which corresponds to theposition 13 in the scheduling table.

FIG. 11E is an explanatory diagram of the scheduling table when thepositions L and the nozzle numbers are associated and registered for thenozzles #1 through #5 for the third pass of “virtual printing 2”. InFIG. 11E, the information in bold outline is information which has beenregistered by overwriting.

The printer driver repeats the above processes until the processes forall the virtual heads finish. In the first reference example, the answerat S109 is “Yes” because the position of the nozzle #1 has attained thefinishing position 18 (=Lf) after the processes (S104 through S107)related to the fourth pass of “virtual printing 2” are finished.Furthermore, in the first reference example, the answer at S111 is “Yes”because the processes for all virtual printing are finished after theprocesses for the fourth pass of “virtual printing 2” are finished, andtherefore the printer driver finishes the process of creating thescheduling table.

<Regarding How to Use the Scheduling Table>

FIG. 12 is an explanatory diagram showing how to use the schedulingtable of the first reference example. Information associating positionsof raster lines with numbers of nozzles which form those raster lines isstored in the scheduling table.

The printer driver first calculates the position of the first nozzlebased on the position of the raster lines and the nozzle numbers foreach piece of information in the scheduling table. If the position ofthe raster line is X and the nozzle number is Y, the position of thefirst nozzle is X−(Y−1)×k. For example, if the position of the rasterline is 7 and the nozzle number is 3, the first nozzle is“1(=7−(3−1)×3)”.

Next, the printer driver extracts, from the information in thescheduling table, the information in which the position of the firstnozzle is the same. For example, four pieces of information areextracted from the scheduling table as information in which the positionof the first nozzle is 1.

The reason that there are only four, and not five, pieces of informationin which the position of the first nozzle is 1 in the scheduling tableis because, as shown in FIG. 11E, the nozzle number 5, corresponding tothe position 13 in the scheduling table, was overwritten by the nozzlenumber 1. Similarly, the reason there are only two pieces of informationin which the position of the first nozzle is 2 in the scheduling tableis because, as shown in FIG. 11D, three pieces of information wereoverwritten.

The printer driver performs rasterization such that image data of rasterlines corresponding to each nozzle are allocated based on the extractedinformation. For example, in pass 1, image data corresponding to a firstraster line is allocated to the nozzle #1, image data corresponding to afourth raster line is allocated to the nozzle #2, image datacorresponding to a seventh raster line is allocated to the nozzle #3,and image data corresponding to a tenth raster line is allocated to thenozzle #4.

However, there are only four pieces of information in the schedulingtable in which the position of the first nozzle is 1, and there is noinformation in the scheduling table related to the position of rasterlines which correspond to the nozzle #5 and the nozzle #6 in pass 1. Inthis case, the printer driver allocates NULL data to the nozzle #5 andthe nozzle #6 as image data.

When the printer driver sends to the printer print data for pass 1generated in this manner, the printer forms four raster lines on thepaper by ejecting ink from the nozzle #1 through the nozzle #4 in pass 1and not ejecting ink from the nozzle #5 and the nozzle #6. In otherwords, in the first reference example, the printer driver allocates NULLdata to the nozzle #5 and the nozzle #6 in pass 1, thereby making thenozzle #5 and the nozzle #6 the unused nozzles.

Similarly, when the printer driver extracts information in which theposition of the first nozzle is 2 and performs rasterization based onthe extracted information, the printer forms two lines on the paper inpass 2 by ejecting ink from the nozzle #1 and the nozzle #2 and notejecting ink from the nozzle #3 through the nozzle #6. In other words,in the first reference example, the printer driver allocates NULL datato the nozzle #3 through the nozzle #6 in pass 2, thereby making thenozzle #3 through the nozzle #6 the unused nozzles.

PROBLEMS IN THE FIRST REFERENCE EXAMPLE

With the first reference example, it is necessary to create a schedulingtable which corresponds to all raster lines before printing. A storagearea for storing the scheduling table must therefore be set aside. InFIG. 8, the total number of raster lines is only 52, but the actualnumber of nozzles is 180, so the amount of data for the scheduling tablefor all the raster lines is extremely large in cases in which there areseveral thousand raster lines in the normal printing region.

Furthermore, the process of extracting only that data needed, as shownin FIG. 12, from among this extremely large amount of data takes a longtime. Also, print data cannot be created until the scheduling table iscomplete, delaying the start of printing.

Accordingly, in the present embodiment, a scheduling table is createdand unused nozzles are determined pass by pass, as described below.

First Embodiment

FIG. 13 is an explanatory diagram of parameters for setting conditionsfor virtual printing in a first embodiment. These parameters for thevirtual printing are determined based on the printing mode and the papersize.

In the present embodiment, when associating the nozzles in a certainpass with the positions of the raster lines which those nozzles willform, the printer driver compares the positions of each nozzle in thatpass with the positions of nozzles in other passes. Then, based on theresults of the comparison, the printer driver creates the schedulingtable for that pass.

Since scheduling tables are created in sequence for each pass, thescheduling tables for passes during upper-end printing are createdbefore scheduling tables for passes during normal printing. Belowfollows a description in order of the creation of a scheduling table.

<Regarding Creation of Scheduling Tables for Upper-End Printing>

FIG. 14 is a flowchart showing a process for creating the schedulingtable for pass m during upper-end printing according to the firstembodiment. The printer driver executes these processes by using thehardware resources of the computer according to a program stored in thememory. FIG. 15A through FIG. 15E are explanatory diagrams of stages inthe process for creating the scheduling table for pass 1. At the bottomof each drawing is shown the scheduling table being created, while atthe top of each drawing conceptual diagrams of the content of processesduring creation of scheduling tables are shown. The scheduling table isrecorded in the memory on the computer. The printer driver creates thescheduling table using the virtual printing parameters for upper-endprinting and the virtual printing parameters for normal printing.

The printer driver initializes the nozzle number i, and sets i=1 (thenumber of the first nozzle in the virtual printing parameters forupper-end printing) (S201). The printer driver then calculates aposition L for the nozzle #1 during pass m (pass 1 being the first)(S202). The position L of the nozzle #i is calculated from the virtualprinting parameters for upper-end printing (i.e., the nozzle pitch k,the carry amount F, the starting position Ls), the nozzle number i, thepass number m, and so on. The position of the nozzle #1 during pass 1 isthe starting position Ls. The printer driver then associates theposition L with the nozzle #i, and registers this in the schedulingtable (S203). The last nozzle is #5, so the printer driver repeats theabove processes until i=5 (S201 through S205).

In other words, a scheduling table is created in which the positions ofthe nozzles and the nozzle numbers are associated for pass m, throughthe processes of step S201 through step S205. During the creation of thescheduling table for pass 1, FIG. 15A shows the scheduling table at thepoint at which the answer at step S204 is “Yes.”

Next, the printer driver calculates the position of the nozzle #1 duringthe next pass (S206). If the position of the nozzle #1 during the nextpass is in the normal printing region (“No” at S207), the schedulingtable for pass 1 is finished. However, the nozzle #1 during pass 2 is inthe position of the second raster line, and is in the upper-end printingregion, so the printer driver process proceeds to step S208.

Next, after initializing the nozzle number i (S208), the printer drivercalculates a position L of the nozzle #i (S209). If that position is inthe upper-end printing region (“Yes” at S210) and the position L hasbeen registered in the scheduling table (“Yes” at S211), then thescheduling data for the position L is deleted. The last nozzle is #5, sothe printer driver repeats the above processes until i=5 (S209 throughS214) If, in the middle of this, the position L of the nozzle #i is inthe normal printing region (“No” at S210), the position of the virtualhead is moved by the carry amount F (S215) and the printer driverprocess returns to step S206.

In other words, the positions of the nozzles for pass m and thepositions of the nozzles for passes after pass m are compared throughthe process of step S209 through step S214. If, as a result of thecomparison, any positions match, the scheduling data for those positionsare deleted.

FIG. 15B shows a scheduling table when the answer is “No” at step S210the first time. Until this point, the positions of the nozzles in pass 2are compared to the scheduling table created as shown in FIG. 15A. As aresult of the comparison, no positions match, and therefore thescheduling table is not changed from the one shown in FIG. 15A.

FIG. 15C shows a scheduling table when the answer is “No” at step S210the second time. Until this point, the positions of the nozzles in pass3 are compared to the scheduling table in FIG. 15B. As a result of thecomparison, no positions match, and therefore the scheduling table isnot changed from the one shown in FIG. 15A.

FIG. 15D shows a scheduling table when the answer is “No” at step S210the third time. Until this point, the positions of the nozzles in pass 4are compared to the scheduling table in FIG. 15C. However, the nozzle #4in pass 4 is not in the upper-end printing region, so that the answer is“No” at S210 when i=4. Furthermore, pass 4 is a dot-forming process innormal printing, so the positions of the nozzles in pass 4 arecalculated from the virtual printing parameters for normal printing(i.e., the nozzle pitch k, the carry amount F, the starting positionLs), the nozzle number i, the pass number, and so on.

FIG. 15E shows a scheduling table when the answer is “No” at step S210the fourth time. Up until this point, the position of the nozzle #1 inpass 5 is compared to the scheduling table shown in FIG. 15D. (Thenozzle #2 in pass 5 is not in the upper-end printing region, so theanswer is “No” at S210 when i=2.) The nozzle #1 in pass 5 is in theposition of the thirteenth raster line, and scheduling data indicating“position:13” is already registered to the scheduling table, so theprinter driver deletes the scheduling data (S212).

The nozzle #1 in pass 6 is in the normal printing region, so in pass 6the answer at S207 is “No,” and the process of creating the schedulingtable for pass 1 is finished. The scheduling table (FIG. 15E) at thispoint thereby becomes the scheduling table for pass 1.

<Regarding Creation of Scheduling Tables for Normal Printing>

FIG. 16 is a flowchart showing a process for creating the schedulingtable for pass m during normal printing according to the firstembodiment. The number of passes for performing upper-end printing isset ahead of time, and in the present embodiment it is until pass 3. Forthis reason, the printer driver executes the following processes frompass 4 on. Scheduling tables for each of passes 4 through 6 are shown atthe bottom of FIG. 17A through FIG. 17C. At the top of each drawing isshown a conceptual diagram of the content of processes when creating thescheduling tables.

First, the printer driver calculates a position L of the nozzle #1during pass m (pass 4 at first) (S301), and determines whether or notthe position is inside the lower-end printing region (S302). If theposition of the nozzle #1 is in the lower-end printing region, theprocess of the printer driver proceeds to the process of creating ascheduling table for lower-end printing, which is described below.However, the nozzle #1 during pass 4 is in the position of the eighthraster line, so the printer driver process proceeds to step S303.

Next, the printer driver initializes the nozzle number i, and sets i=1(the number of the first nozzle in the virtual printing parameters fornormal printing) (S303). The printer driver then calculates a position Lfor the nozzle #1 during pass m (pass 4 being the first) (S304). Theprocess in step S304 the first time is the same as the process in stepS301, so the process in step S304 the first time may be omitted. Theposition L of the nozzle #i is calculated from the virtual printingparameters for normal printing (i.e., the nozzle pitch k, the carryamount F, the starting position Ls), the nozzle number i, the passnumber m, and so on. The printer driver then associates the position Lwith the nozzle #i, and registers this in the scheduling table (S305).The last nozzle is #5, so the printer driver repeats the above processesuntil i=5 (S304 through S307).

In other words, a scheduling table is created in which the positions ofthe nozzles and the nozzle numbers are associated for pass m, throughthe process of step S303 through step S307. For example, a schedulingtable for pass 4 is created as shown at the bottom of FIG. 17A.

It should be noted that, after a scheduling table for pass 9 has beencreated, the answer is “Yes” at step S302 when the scheduling table forpass 10 is attempted to be created. In this case, the printer driverprocess proceeds to the process of creating a scheduling table forlower-end printing. The scheduling tables for passes on or after pass 10are thereby created by the process for creating scheduling tables forlower-end printing.

<Regarding Creation of Scheduling Tables for Lower-End Printing>

FIG. 18 is a flowchart showing a process for creating the schedulingtable during lower-end printing according to the first embodiment.Unlike the cases of upper-end printing or normal printing describedabove, during lower-end printing, a dummy scheduling table is created(S400) before creating scheduling tables for each pass, and then thescheduling tables for each pass are created based on this dummyscheduling table (S500).

FIG. 19 is a flowchart showing a process for creating a dummy schedulingtable. FIG. 20A through FIG. 20C are conceptual diagrams for explainingthe dummy scheduling table.

The dummy scheduling table indicates the positions of raster linesformed in the lower-end printing region by passes after pass 9, asthough normal printing were performed after pass 9. For this reason,during the process for creating the dummy scheduling table, the virtualprinting parameters for normal printing are used.

First, the printer driver assumes that the carrying process of normalprinting has been performed after the last pass (pass 9) for normalprinting, calculates a position L of the nozzle #1 in pass 10′ (S401),and determines whether or not that position is in the lower-end printingregion (S402). The position of the nozzle #1 in pass 10′ is the positionof the thirty-eighth raster line, so the answer at step S402 is “No.”

Next, the printer driver initializes the nozzle number i, and sets i=1(S403). The printer driver then calculates a position L for the nozzle#1 during pass m (pass 10′ being the first) (S404). When i=1, theprocess in step S404 is the same as the process in step S401, so theprocess in step S404 may be omitted. The position L of the nozzle #i iscalculated from the virtual printing parameters for normal printing(i.e., the nozzle pitch k, the carry amount F, the starting positionLs), the nozzle number i, the pass number m, and so on. If the positionof the nozzle #i is in the lower-end printing region (“Yes” at S405),the printer driver registers the position L in the dummy schedulingtable (S406). In the dummy scheduling table, there is no need toassociate anything with the nozzle numbers, unlike the scheduling tablesdescribed until now. For this reason, the amount of data in the dummyscheduling table is smaller compared to the scheduling tables. Theprinter driver repeats these processes until i=5, since the last nozzleis #5 (S404 through S408), and registers the positions of each nozzle inthat pass in the dummy scheduling table.

When repeating the processes in step S404 through step S408, if aposition L of a nozzle is outside the lower-end printing region (“No” atS405), then the printer driver interrupts registration of the position Lof the nozzle in that pass, and proceeds to step S409. In step S409, thecarrying process of normal printing is assumed to have been performedbefore performing the next pass, and the position L of the nozzle #1 inthe next pass is calculated (S401). In this way, the positions of thenozzles are registered in the dummy scheduling table for the next passas well (S401 through S409). The dummy scheduling table thus createdindicates the positions of the raster lines to be formed in thelower-end printing.

The pass 12 is performed through normal printing, and if the carryingprocess of normal printing is further performed, the position of thenozzle #1 is the position of the fifty-third raster line. For thisreason, the answer at step S402 is “Yes,” and the creation of the dummyscheduling table is finished. The printer driver then uses the dummyscheduling table at this point (FIG. 20C) to perform the process forcreation of a scheduling table for each of the passes.

FIG. 21 is a flowchart showing a process for creating scheduling tablesfor each pass based on the dummy scheduling table. FIG. 22A through FIG.22C are conceptual diagrams for explaining the scheduling tables foreach pass. As described below, the printer driver compares the positionsof the nozzles in each pass in the lower-end printing with the dummyscheduling table and creates scheduling tables for each pass based onthe results of the comparison.

The printer driver first initializes the nozzle number i, and sets i=1(the number of the first nozzle in the virtual printing parameters forlower-end printing) (S501). The printer driver then calculates aposition L for the nozzle #1 during pass m (pass 10 being the first)(S502). The position L of the nozzle #i is calculated from the virtualprinting parameters for lower-end printing (i.e., the nozzle pitch k,the carry amount F, the starting position Ls), the nozzle number i, thepass number m, and so on. The position of the nozzle #1 during pass 10is the starting position Ls.

Next, the printer driver compares the calculated position L and thedummy scheduling table (S503). Specifically, the printer driver compareswhether or not the calculated position L matches any positionsregistered in the dummy scheduling table.

If the position L is present in the dummy scheduling table (“Yes” atS504), the printer driver associates the position L and the nozzle #1and registers them in the scheduling table for pass m (S505), in orderto form a raster line at the position L during lower-end printing. Theprinter driver then deletes the registration of the position L from thedummy scheduling table. This is to speed up processing when repeatingstep S503 later.

If, on the other hand, the position L is not present in the dummyscheduling table (“No” at S504), there is no need to form a raster lineat the position L in the lower-end printing, so the printer driverprocess proceeds to step S507, without performing the process forregistering to the scheduling table. The last nozzle is #5, so theprinter driver repeats the above processes until i=5 (S502 throughS508). In other words, a scheduling table is created in which thepositions of the nozzles and the nozzle numbers are associated for passm, through the processes of step S501 through step S508.

In the top of FIG. 22A through FIG. 22C, the positions of the nozzles ineach pass and the positions registered in the dummy scheduling data areconceptually shown. Of the circles indicating registered content of thedummy scheduling table, black circles indicate registered positions,while white circles indicate positions which have been deleted in stepS506. As shown in FIG. 22A, the positions of the nozzle #1 through thenozzle #5 in pass 10 are registered to the dummy scheduling table. Forthis reason, the scheduling table for pass 10 is made up of five piecesof information, as shown at the bottom of FIG. 22A. On the other hand,when creating the scheduling table for pass 10, the positions of thefive pieces of information in the dummy scheduling table are deleted instep S506. As a result, the dummy scheduling table used when creatingthe scheduling table for pass 11 is as shown at the top of FIG. 22B. Asa result of comparing the positions of the nozzles in pass 11 with thedummy scheduling table, the scheduling table for pass 11 is made up ofthe two pieces of information as shown at the bottom of FIG. 22B.Similarly, the scheduling table for pass 12 is made up of four pieces ofinformation, as shown at the bottom of FIG. 22C.

Furthermore, when the scheduling table for pass 12 is finished, theposition of the nozzle #1 reaches the finishing position Lf (=40; seeFIG. 13), so creation of the scheduling table is finished.

<Regarding Rasterization>

The created scheduling tables are used in rasterization. The schedulingtables of the present embodiment are created in the order of printingfor each pass. Therefore, unlike the case shown in the reference exampledescribed above, the printer driver of the present embodiment can beginrasterization and can begin sending print data for each pass for whichrasterization is complete, before finishing creation of schedulingtables for all passes. This point is described below.

FIG. 23A is an explanatory diagram showing image data (image data afterhalftoning) before rasterizing. The squares in the drawing indicatepixels which make up the image. The numbers within the squares indicatethe number of the pixel. In order to simplify the description, thenumber of pixels arranged in the movement direction is 16 pixels.

Halftoned image data is made up of pixel data with 2 bits of data perpixel. For this reason, assuming that image data is stored in a memorythat stores one byte of information per address, pixel data for fourpixels is stored per address. The bold rectangles in the drawingindicate pixels which correspond to the pixel data stored in one addressof the memory.

The “raster data” in the drawing is pixel data which corresponds toraster lines, or in other words, a plurality of pieces of pixel datawhich correspond to a plurality of pixels arranged in the movementdirection. Here, one piece of “raster data” is 4-byte data, whichincludes 16 pieces of pixel data.

FIG. 23B is an explanatory diagram showing the order of pixel databefore rasterizing. Each rectangle in the drawing indicates one byte ofdata (pixel data for four pixels). The circles in the rectangle indicatepixel data stored in the one byte of data, and the numbers inside thecircles indicate the numbers of the pixels which correspond to the pixeldata. For example, pixel data which corresponds to the first through thefourth pixels is stored in the first byte of data.

Unrasterized pixel data is stored in the memory in the order of theraster lines. Put another way, the pixel data is stored in the order ofthe raster lines in contiguous addresses in the memory. However,printing is not performed by the printer in this order. For example, inpass 1, the first, fourth, seventh, tenth, and thirteenth raster linesare formed, so printing is not performed in the order of the rasterlines. Accordingly, the printer driver needs to rearrange the pixel datainto an order appropriate for printing, through rasterization.

FIG. 24A is an explanatory diagram showing a rasterizing process forcreating print data for pass 1. When interlaced printing is performed bymoving the head from left to right, the first pixel data, which areindicated by the bold circles in the drawing, are needed in order toform dots in the first pixels. However, before rasterization, the firstpixel data, which are indicated by the bold circles, are not stored incontiguous addresses in the memory.

The printer driver accordingly rearranges the pixel data into the ordershown by the arrows in the drawing. With this, the pixel data shown bythe bold circles are stored in addresses contiguous in the memory. Theprinter driver, at this point, references the scheduling table anddecides which raster data to extract the pixel data from. When creatingthe print data for pass 1, the scheduling table (FIG. 15E) for pass 1 isreferenced, and pixel data from the first, fourth, seventh, and tenthraster data is extracted from the left.

FIG. 24B is an explanatory diagram showing the order of pixel data afterrasterizing, the order of pixel data being contained in the print datafor pass 1. The first byte of pixel data is extracted from the firstraster data, and associated with the nozzle #1. The next byte of pixeldata is extracted from the fourth raster data, and associated with thenozzle #2. In this way, pixel data is associated one byte at a time fromthe first nozzle (the nozzle #1) until the last nozzle (the nozzle #6).Then, the pixel data associated with the first nozzle is arranged afterthe pixel data associated with the last nozzle. By repeating this, thepixel data included in the print data for pass 1 is created.

The NULL data in the drawing is not the pixel data extracted from theimage data, but data created by the printer driver, and is made up ofpixel data indicating non-ejection of ink (non-formation of dots). NULLdata is allocated to nozzles which are not associated with a position inthe scheduling table. Here, NULL data is associated with the nozzle #5and the nozzle #6.

The printer driver then sends to the printer the print data for the passfor which rasterization has finished.

FIG. 25 is an explanatory diagram of a dot-forming process based on theprint data. The head 41 ejects ink based on the data transferred fromthe unit control circuit 64, thereby forming dots on the paper. In thedrawing, three dots have been formed by ink droplets ejected based onthe first through third pixel data.

The unit control circuit 64 is provided with a timing generating section642 and a double buffer 644. The timing generating section 642 generatesa timing signal in accordance with a signal from the linear encoder 51and outputs it to the double buffer 644. Two buffers are provided in thedouble buffer 644 for storing pixel data. Each buffer can store onebyte's worth of data per nozzle (i.e., four pixels' worth of pixeldata). Every time a timing signal is received, the double buffer 644serially transfers, to the head 41, one pixel's worth of pixel data forall nozzles, among the pixel data which are stored in the buffer.

Next, operation when ink droplets are ejected based on the print data isdescribed.

First, the printer driver sends the print data to the printer 1. Theprint data contains the pixel data needed for at least a single pass.Each pixel data indicates a dot forming condition for one pixel (i.e.,large dot, medium dot, small dot, no dot), and has a data amount of twobits. The pixel data received by the printer 1 are in an orderappropriate for printing because of the rasterization performed by theprinter driver (described above), and the printer 1 stores in the memory63 the pixel data according to this order. One address in the memory 63can stored one byte of information, so four pixels' worth of pixel datacan be stored per address.

The unit control circuit 64 stores the pixel data stored in contiguousaddresses in the memory 63 into one of the buffers of the double buffer644 through a burst transfer. Here, six bytes' worth of pixel data isburst transferred to the double buffer 644 from the memory 63. Pixeldata corresponding to adjacent nozzles are stored in adjacent addressesin the memory 63 because of the rasterization of the printer driver.Four bytes' worth of pixel data for all nozzles can therefore be bursttransferred.

Next, the unit control circuit 64 drives the carriage motor 32 and movesthe carriage 31 in the movement direction. Every time the carriage 31moves 1/180 of an inch, the linear encoder 51 outputs a pulse signal ofone cycle. The timing generating section 642 generates a timing signalin accordance with a signal from the linear encoder 51.

When the first timing signal is received, the double buffer 644 performsa serial transfer to the head 41 of the pixel data stored in a firstregion indicated by a bold line in the drawing. Pixel data correspondingto the first pixel for all the nozzles are stored in this region. Thehead 41 ejects (or does not eject) ink from each nozzle according to thefirst pixel data. As a result, a dot is formed which corresponds to thefirst pixel data in the first pixel (pixel #1) on the paper.

Since the carriage 31 is moving in the movement direction while ink isbeing ejected from the head 41, the double buffer 644 continues toreceive the prescribed timing signals. When the next timing signal isreceived, the double buffer 644 performs a serial transfer to the head41 of the pixel data that are stored in a second region, and the head 41ejects ink in accordance with the pixel data. In this way, ink isejected from the head 41 intermittently in accordance with the timingsignal.

The unit control circuit 64 transfers a set of pixel data to one of thebuffers of the double buffer 644, and then transfers the next set ofpixel data to the other buffer from the memory 63. The double buffer 644can thereby transfer to the head 41 the pixel data in the fourth regionand then transfer to the head 41 the pixel data in the fifth regionwhich is in the other buffer. After transferring to the head 41 thepixel data in the fourth region, the unit control circuit 64 transfersthe next set of pixel data (the ninth through twelfth pixel data) fromthe memory 63 to the first region through the fourth region of thedouble buffer. The unit control circuit 64 thereby transfers pixel datain an alternating manner to the two buffers of the double buffer 644.

Note that nozzle groups are provided to the head 41 for each color, andthat the double buffer 644 is provided for each nozzle group, or inother words, for each color. However, the timing generating section 642generates a common timing signal for the plurality of the double buffer644 provided for each color. As a result, ink droplets are ejected at acommon timing from the nozzle groups of each color.

The print data for pass 1 associates NULL data to the nozzle #5 and thenozzle #6. NULL data is therefore stored in the regions of the doublebuffer corresponding to the nozzle #5 and the nozzle #6. As a result,even if this data is transferred to the head, the nozzle #5 and thenozzle #6 do not eject ink. In other words, the nozzle #5 and the nozzle#6 are nozzles which do not eject ink (the unused nozzles) during pass1.

In the first embodiment, described above, print data is not created andsent after finishing creation of all the scheduling tables, but insteadscheduling tables are created for each pass and rasterization isperformed pass by pass, and then the print data for each pass is sent tothe printer in sequence. The printer can thereby speed up the start ofprinting.

Second Embodiment

<Regarding Partial Overlap Printing>

In the first embodiment described above, only one nozzle formed oneraster line. However, if a certain nozzle suffered from faulty ejection,the raster line formed by that nozzle would be defective, and theresulting printed image would have stripes. In particular, nozzles whichare positioned at the ends of the nozzle groups (the nozzle #1 and thenozzle #6 in the case of the model example with six nozzles) are proneto faulty ejection, which entails a risk of defective raster lines beingformed by those nozzles. Accordingly, specific raster lines are formedby two or more nozzles in “partial overlapped printing,” which isdescribed below, so even if a nozzle suffers from faulty ejection,defective raster lines can be reduced.

FIG. 26A and FIG. 26B are explanatory diagrams of partial overlappedprinting. FIG. 26A shows the positions of the head (or nozzle group) andhow dots are formed in passes 1 to 5. FIG. 26B shows the positions ofthe head and how dots are formed in passes 1 to 6. For the sake ofdescription, there are triangular and square nozzles and dots, but inactuality all nozzles and dots are circular.

In partial overlapped printing, a nozzle which is positioned on the endupstream in the carrying direction from the nozzle group (also called a“POL-bottom nozzle”) and a nozzle which is positioned on the enddownstream in the carrying direction from the nozzle group (also calleda “POL-top nozzle”) perform the same function as one nozzle positionedin a central portion of the nozzle group. For example, in FIG. 26A andFIG. 26B, the nozzle #1 and the nozzle #6 only form half dots comparedto the nozzle #2 through the nozzle #5. However, the number of nozzleswhich can eject ink in FIG. 26A and FIG. 26B (six) is greater comparedto the number of nozzles which can eject ink in FIG. 7A and FIG. 7B(five).

In partial overlapped printing, the nozzle which is positioned at theends upstream in the carrying direction forms dots intermittently, everyother dot. In other passes, the nozzle positioned at the end downstreamin the carrying direction forms dots such that the already formedintermittent dots are interpolated (i.e., between the dots). The twonozzles positioned at the ends thereby perform the same function as onenozzle positioned in the central portion. For example, in FIG. 26A andFIG. 26B, the nozzle #6 forms dots (the dots shown as squares) everyother dot in a certain pass, and then the nozzle #1 forms dots (the dotsshown as triangles) in another pass, filling the space between the dots,thereby completing a single raster line. Here, the dots shown as squaresare formed in odd pixels on the paper, and the dots shown as trianglesare formed in even pixels on the paper.

With partial overlapped printing, a drop in the image quality of rasterlines formed by a plurality of nozzles due to variations in ink ejectioncan be suppressed. In particular, variations in ink ejection by nozzleson the ends is large compared with nozzles in the central portion, so ifa raster line formed by the nozzles on the ends is formed by a pluralityof nozzles, an effect can be achieved of suppressing a drop in imagequality.

FIG. 27 is an explanatory diagram of upper-end printing and lower-endprinting in partial overlapped printing.

In the upper-end printing of the first embodiment (see FIG. 8), thenozzle #5 in pass 1, the nozzle #3 in pass 2, and the nozzle #6 in pass3 are nozzles which do not eject ink. On the other hand, with upper-endprinting in partial overlapped printing of the second embodiment, ink isalso ejected from these nozzles, in order to interpolate theintermittent dots formed by the nozzle #1 in normal printing.

Furthermore, in the lower-end printing of the first embodiment (see FIG.8), the nozzle #1 in pass 10, the nozzle #4 in pass 11, and the nozzle#2 in pass 12 each formed a raster line using a single nozzle. On theother hand, with lower-end printing in partial overlapped printing ofthe second embodiment, these nozzles form dots only in even pixels, inorder to interpolate the intermittent dots formed by the nozzle #1 innormal printing.

<Regarding Parameters>

FIG. 28 is an explanatory diagram of parameters for setting conditionsfor virtual printing in a second embodiment. The parameters surroundedby a bold line in the drawing are parts which differ from the parametersin the first embodiment (see FIG. 13). With the present embodiment,parameters “for the POL-top nozzle” are provided as parameters forvirtual printing of partial overlapped printing by the nozzle at the enddownstream in the carrying direction. Furthermore, parameters “for thePOL-bottom nozzle” are provided as parameters for virtual printing ofpartial overlapped printing by the nozzle at the end upstream in thecarrying direction. Additionally, the nozzle #1 forms dotsintermittently in partial overlapped printing, so the first nozzle inthe parameters for normal printing is not the nozzle #1, but rather thenozzle #2. Further, since the number of nozzles which can eject inkduring normal printing is six, the last nozzle in upper-end printing andlower-end printing is consequently the nozzle #6.

<Regarding Creation of Scheduling Tables for Upper-End Printing>

FIG. 29 is a flowchart showing a process for creating the schedulingtable for pass m during upper-end printing according to the secondembodiment. FIG. 30A through FIG. 30C are explanatory diagrams of stagesin the process for creating the scheduling table for pass 1.

In the second embodiment, the processes from step S201 through step S215(see FIG. 14) are the same as for the first embodiment, described above,so their description is omitted. In the second embodiment, after theanswer at step S207, described above, is “No,” the printer driverprocess proceeds to the following step S216.

Furthermore, in the second embodiment, the first nozzle in normalprinting is the nozzle #2, so in step S208, the nozzle number isinitialized to i=2. As a result, the scheduling data of “position:13” asshown in FIG. 15E is not deleted. On the other hand, the last nozzle inthe upper-end printing is the nozzle #6, so the position of the nozzle#6 in pass 1 and the position of the nozzle #2 in pass 5 match, so thescheduling data of “position:16” is deleted. The scheduling table whenthe answer at step S217 is “No” in the second embodiment is therefore asshown in FIG. 30A.

After the processes of step S201 through step S215, the printer drivercalculates a position L of the POL-top nozzle (the nozzle #1) based onthe parameters “for the POL-top nozzle” (S216). The position L which iscalculated at first (=8) is equivalent to the position of the nozzle #1during pass 4. The printer driver then determines whether or not theposition is in the upper-end printing region (S217). Since the positionL calculated at first (=8) is in the upper-end printing region, theprinter driver process proceeds to step S218.

Next, the printer driver determines whether or not the position L isregistered in the scheduling table (S218). Since the position Lcalculated at first (=8) is not registered in the scheduling table, theposition of the virtual head is moved by the carry amount F (S220) andthe printer driver process returns to step S216. The scheduling table atthis point is as shown in FIG. 30B.

The position L which is calculated next (=13) is equivalent to theposition of the nozzle #1 during pass 5. The position L is registered inthe scheduling table, so the answer at step S218 is “Yes.” In this case,the printer driver rewrites the information of the position L in thescheduling table and adds information to the effect that the recordingposition is odd pixels (S219). Note also that in partial overlappedprinting, the POL-bottom nozzle forms dots in odd pixels on the paper.The scheduling table at this point is as shown in FIG. 30C.

Similarly, the printer driver moves the position of the virtual head bythe carry amount F (S220) and determines whether or not the position Lwhich is equivalent to the position of the nozzle #1 during pass 6 isregistered in the scheduling table (S218). Thereafter, the position Lequivalent to the position of the nozzle #1 during pass 7 is calculated(S216), and that position L is not in the upper-end printing region(S217), so the printer driver finishes the process for creating thescheduling table for pass 1.

<Regarding Creation of Scheduling Tables for Normal Printing>

FIG. 31 is a flowchart showing a process for creating the schedulingtable for pass m during normal printing according to the secondembodiment. FIG. 32A through FIG. 32C are explanatory diagrams of stagesin the process for creating the scheduling table for pass 4.

In the second embodiment, the processes from step S301 through step S307are the same as for the first embodiment (see FIG. 16), described above,so their description is omitted. In the second embodiment, after theanswer at step S206, described above, is “Yes,” the printer driverprocess proceeds to the following step S308.

First, the printer driver calculates a position L of the nozzle (thePOL-top nozzle) positioned at the end downstream in the carryingdirection of the nozzle group during pass m, based on the parameters“for the POL-top nozzle” (S308). The printer driver then associates theposition L with the POL-top nozzle (here, the nozzle #1), and registersthis in the scheduling table (S309). At this point, the printer driveradds information to the effect that the recording position is evenpixels. Note also that in partial overlapped printing, the POL-topnozzle forms dots in even pixels on the paper. The scheduling table atthis point is as shown in FIG. 32B.

Next, the printer driver calculates a position L of the nozzle (thePOL-bottom nozzle) positioned at the end upstream in the carryingdirection of the nozzle group during pass m, based on the parameters“for the POL-bottom nozzle” (S310). The printer driver then associatesthe position L with the POL-bottom nozzle (here, the nozzle #6), andregisters this in the scheduling table (S311). At this point, theprinter driver adds information to the effect that the recordingposition is odd pixels. Note also that in partial overlapped printing,the POL-bottom nozzle forms dots in odd pixels on the paper. Thescheduling table at this point is as shown in FIG. 32C.

<Regarding Creation of Scheduling Tables for Lower-End Printing>

As in the case of lower-end printing in the first embodiment, describedabove, before creating scheduling tables for each pass for lower-endprinting in the second embodiment, a dummy scheduling table is created(S400). The process for creating the dummy scheduling table of thesecond embodiment is the same as that of the first embodiment, describedabove, and description thereof is omitted. However, as a consequence ofthe number of nozzles which can eject ink in normal printing becomingsix, the first nozzle during creation of the dummy scheduling table isnot the nozzle #2 but rather the nozzle #1, and the last nozzle is notthe nozzle #5, but rather the nozzle #6. Position:53-55 is assumed asbeing included in the lower-end printing region. As a result, the dummyscheduling table of the second embodiment is a dummy scheduling data ofpositions 53 through 55 added to the dummy scheduling table in FIG. 20C.

FIG. 33 is a flowchart showing a process for creating the schedulingtable for each pass during lower-end printing according to the secondembodiment. FIG. 34A through FIG. 34D are explanatory diagrams of stagesin the process for creating the scheduling table for pass 10.

In the second embodiment, the processes from step S501 through step S508are the same as for the first embodiment (see FIG. 21), described above,so their description is omitted. In the second embodiment, after theanswer at step S507, described above, is “Yes,” the printer driverprocess proceeds to the following step S509. The scheduling table atthis point is as shown in FIG. 34A.

First, the printer driver calculates a position L of the POL-bottomnozzle (the nozzle #6) based on the parameters “for the POL-bottomnozzle” (S509). Since the position L calculated at first (=23) is in thenormal printing region (“No” at S510), the printer driver moves theposition of the virtual head by the carry amount F (S511) and theprinter driver process returns to step S509. Until the POL-bottom nozzleis positioned in the lower-end printing region, the position of thevirtual head is moved by the carry amount F.

When the virtual head is in the position equivalent to pass 7, theposition L of the POL-bottom nozzle (=38) is in the lower-end printingregion (“Yes” at S510), so the printer driver determines whether or notthe position L is registered in the scheduling table (S512). Here, theposition L (=38) is registered in the scheduling table (“Yes” at S512),so the information on the position L in the scheduling table isrewritten and information is added to the effect that the recordingposition is even pixels (S513). Note also that in partial overlappedprinting, the POL-top nozzle forms dots in even pixels on the paper. Thescheduling table at this point is as shown in FIG. 34B.

The printer driver then moves the position of the virtual head by thecarry amount F (S511) and calculates the position L of the POL-bottomnozzle equivalent to pass 8 (S509). However, this position L (=43) isnot registered in the scheduling table, so the answer at S512 is “No.”The scheduling table at this point is as shown in FIG. 34C. Similarly,the printer driver then moves the position of the virtual head by thecarry amount F (S511) and calculates the position L of the POL-bottomnozzle equivalent to pass 9 (S509). However, this position L (=48) isnot registered in the scheduling table, so the answer at step S512 is“No.” The scheduling table at this point is as shown in FIG. 34D. Theposition of the nozzle #1 during pass 9 has reached the finishingposition of the parameters “for the POL-bottom nozzle,” so the answer atstep S514 is “Yes,” so the printer driver finishes the process forcreating the scheduling table for pass 10.

<Regarding Rasterization>

The scheduling table created in the second embodiment is also used inrasterization. However, in the second embodiment, the information of the“scanning direction position” in the scheduling table is taken intoconsideration and rasterization is performed.

FIG. 35A is an explanatory diagram showing a rasterizing process forcreating print data for pass 4. FIG. 35B is an explanatory diagramshowing the order of pixel data after rasterizing, said order of pixeldata being contained in the print data for pass 4. FIG. 36 is aconceptual diagram of a process up until pass 4 is performed.

In almost the same way as in the case of the first embodiment, theprinter driver rearranges the pixel data in the order shown by the arrowin FIG. 35A, based on the scheduling table (FIG. 32C) for pass 4 of thesecond embodiment. The pixel data corresponding to the nozzle #1 throughthe nozzle #6 is thereby extracted from the eighth, eleventh,fourteenth, seventeenth, twentieth, and twenty-third raster data, andthe print data is created. The extraction of the pixel data from theraster data is almost the same as in the case of the first embodiment,so the description thereof is omitted.

In the second embodiment, information that “scanning direction position:even numbers” is registered in the scheduling data of “position: 8” inthe scheduling table for pass 4. In such a case, the printer driverapplies a mask to the odd-numbered pixel data in order only to extracteven-numbered pixel data, when extracting the pixel data from the eighthraster data. When creating the print data, the printer driver rewritesthe pixel data to which the mask has been applied to NULL data. A maskis thereby applied to the first and third pixel data when extracting thefirst pixel data from the eighth raster data, and as a result, the firstbyte of pixel data in the print data contains two bits of NULL data, thesecond pixel data (two bits), two bits of NULL data, and the fourthpixel data (two bits), in this order (see FIG. 35B).

In the second embodiment, information that “scanning direction position:odd numbers” is registered in the scheduling data of “position: 23” inthe scheduling table for pass 4. In such a case, the printer driverapplies a mask to the even-numbered pixel data in order only to extractodd-numbered pixel data, when extracting the pixel data from thetwenty-third raster data. When creating the print data, the printerdriver rewrites the pixel data to which the mask has been applied toNULL data.

When sending to the printer the print data thus created, dots are notformed in pixels which correspond to the NULL data, so during pass 4,the nozzle #1 forms dots intermittently in the even pixels, and thenozzle #6 forms dots intermittently in the odd pixels.

Note that here pass 4 is described, but in other passes, too, ifinformation on the “scanning direction position” is registered in thescheduling table, the same rasterization is performed. The partialoverlapped printing of FIG. 27 is achieved by executing each pass inthis way.

Other Embodiments

The foregoing embodiment described primarily a printer. However, it goeswithout saying that the foregoing description also includes thedisclosure of printing apparatuses, recording apparatuses, liquidejection apparatuses, printing methods, recording methods, liquidejection methods, printing systems, recording systems, computer systems,programs, recording media storing programs, display screens, screendisplay methods, and methods for producing printed material, forexample.

Also, a printer, for example, serving as an embodiment was describedabove. However, the foregoing embodiment is for the purpose ofelucidating the present invention and is not to be interpreted aslimiting the present invention. The present invention can of course bealtered and improved without departing from the gist thereof andincludes functional equivalents. In particular, the embodimentsmentioned below are also included in the invention.

<Regarding the Nozzles>

In the foregoing embodiment, ink was ejected using piezoelectricelements. However, the method for ejecting liquid is not limited tothis. Other methods, such as a method for generating bubbles in thenozzles through heat, may also be employed.

===Overview===

(1) With the printing system described above, a computer 110 (an exampleof a print control apparatus) in which a printer driver is installed,and a printer 1 (an example of a printing apparatus) are provided. Theprinter driver (more accurately, the computer 110 in which the printerdriver is installed) creates the print data (FIG. 2, FIG. 24A, and FIG.24B) by the rasterization (a process of rearranging a plurality ofpieces of pixel data which make up an image data (see FIG. 23A, FIG.23B)). The printer 1 alternately repeats a dot-forming process (S003(see FIG. 5)) based on the print data and a carrying process (S004),thereby forming on a paper S (an example of a medium) a plurality ofraster lines (an example of a row of dots) arranged in a carryingdirection. Here, the dot-forming process is a process for forming rasterlines by ejecting ink from a plurality of nozzles moving in a movementdirection, and is also called a “pass.” The carrying process is aprocess for carrying the paper S in the carrying direction with respectto the nozzles.

Incidentally, when performing rasterization, the pixel data needs to berearranged based on the position, in the carrying direction on the paperS, of the raster lines formed by the nozzles. Accordingly, in the caseof the first reference example and in the case of the presentembodiments (the first and second embodiments), the printer driverperforms rasterization, referencing the scheduling table.

However, in the case of the first reference example, the positions ofthe nozzles in all the passes which are repeatedly performed are storedas scheduling tables, so the amount of data of the scheduling tablesbecomes extremely large. Further, a process for extracting specific datafrom such a scheduling table takes a long time. Moreover, print datacannot be created until the scheduling table is complete, delaying thestart of printing.

Accordingly, in the present embodiments described above, every timeprint data for a certain pass is to be created, the printer driverstores in a scheduling table the positions in the carrying direction onthe paper S of the raster lines which are to be formed by the nozzlesduring that pass. For example, in the first embodiment, as thescheduling table for pass 4, the position 8, the position 11, theposition 14, the position 17, and the position 20 are stored (see FIG.17A). Next, the printer driver extracts, from the image data, the pixeldata corresponding to the positions in the scheduling table and performsrasterization (see FIG. 24A) to create the print data (see FIG. 24B).After creating, for example, the print data for pass 4 in this way, thescheduling table for pass 4 becomes unnecessary, so the printer driverstores, in the memory, the scheduling table for the next pass 5.

With the present embodiments, scheduling tables can be created for eachdot-forming process (each pass).

As a result, the amount of data of the scheduling tables of the presentembodiment (see, for example, FIG. 15E, FIGS. 17A through 17C, and FIGS.22A through 22C) is smaller compared to the amount of data of thescheduling tables of the first reference example (see, for example, FIG.12). With the present embodiment, the scheduling tables for each of thepasses are created directly, so a process for extracting necessary datafrom a plurality of scheduling data, as in the first reference example(see FIG. 12), is unnecessary, so the time to create scheduling tablesfor each pass can be reduced. Furthermore, for example, after creatingthe scheduling table for pass 1, the print data for pass 1 can becreated without waiting for the creation of the scheduling tables forother passes, so printing can be started quicker.

(2) Note that with the present embodiments, the number of times thecomparing process (S105, etc., and S211, etc.) is performed untilscheduling tables for all the passes are created is greater than thefirst reference example. For this reason, with the present embodiments,the amount of time to create the scheduling tables for all the passes islonger than in the first reference example. However, even if thecreation of scheduling tables for later passes (e.g., pass 10, etc.) isslower in the present embodiments than in the first reference example,it is sufficient if the scheduling table for that pass is created andthe print data for that pass is created before that pass is performed,so nothing happens such as the completion of printing becoming slower.

Therefore, in the present embodiments, while the printer 1 is performinga certain pass based on the print data (e.g., pass 1), the printerdriver creates the print data for the pass to be performed thereafter(e.g., the next pass).

(3) In the present embodiments described above, the comparing process isperformed in which the positions of the nozzles during different passesin upper-end printing (more accurately, the positions in the carryingdirection on the paper S of the raster lines formed by the nozzles) arecompared (S211), and if any match (“Yes” at S211), those positions aredeleted from the table (S212). For example, in FIG. 15B the positions ofthe nozzles during pass 1 and pass 2 are compared, and in FIG. 15C thepositions of the nozzles during pass 1 and pass 3 are compared.(However, in the present embodiments, the positions do not match.) Thisis to prevent the same raster line from being formed twice in upper-endprinting.

(4) In the present embodiments, not only are the passes in upper-endprinting compared, but positions of nozzles in passes for the upper-endprinting and positions of nozzles in passes for normal printing arecompared as well. If there are positions that match, then thosepositions are deleted from the scheduling table for passes in theupper-end printing. As a result, if a raster line can be formed both bya nozzle in a pass in the upper-end printing and by a nozzle in a passin the normal printing, that line will be formed using the pass in thenormal printing. By giving priority to nozzles in a pass performingnormal printing, the number of raster lines formed through normalprinting is increased, thereby improving the quality of the printedimage.

(5) In the second embodiment described above, as a result of performingpartial overlapped printing, for example, the nozzle #6 in pass 4 formsdots in the odd pixels (an example of specific positions in the movementdirection), and when performing pass 7, the nozzle #1 (an example of another nozzle) forms dots in the even pixels, such that the spacesbetween the dots formed in the odd pixels are filled in.

When partial overlapped printing is thus performed, the printer driverassociates “odd”, which is the recording position in the scan direction,with the position of the nozzle #6 and stores this in the schedulingtable (FIG. 32C). The twenty-third raster line in FIG. 27, for example,can thus be prevent from being formed twice.

(6) With the second embodiment, described above, nozzles which eject inkintermittently in normal printing (e.g., the nozzle #1) are positionedat the ends in the carrying direction of the nozzles which eject ink.This is because nozzles positioned at the ends are prone to faultyejection. This is not a limitation, however. For example, the nozzlespositioned in the central portion of the nozzle group may performpartial overlapped printing by forming dots intermittently.

(7) In the present embodiments described above, the print controlapparatus for controlling the printing apparatus was a computer in whicha printer driver is installed. In other words, the print controlapparatus was provided separately to the printing apparatus.

(8) However, this is not a limitation. For example, the functionality ofthe printer driver may be provided to the printer 1. The CPU 62 mayfunction as the print control apparatus, controlling a printingapparatus comprising the carrying unit 20, the carriage unit 30, and theheat unit 40. In this case, the print control apparatus and the printingapparatus may be provided as a single unit to the printer 1, the printer1 thereby being the printing system in a single unit.

1. A printing method comprising: creating print data by rearranging anorder in which a plurality of pieces of pixel data which make up imagedata are arranged; and based on the print data, alternately repeating adot-forming process for forming, on a medium, a row of dots along amovement direction by ejecting ink from a plurality of nozzles whichmove in the movement direction and a carrying process for carrying themedium in a carrying direction with respect to the nozzles, to form, onthe medium, a plurality of the rows of dots arranged in the carryingdirection, wherein, every time the print data for performing adot-forming process is to be created, positions, on the medium in thecarrying direction, of the rows of dots to be formed by the nozzlesduring that dot-forming process are calculated and stored in a table, acomparing process is performed in which positions, on the medium in thecarrying direction, of the rows of dots to be formed by the nozzlesduring an other dot-forming process are compared with the positionsstored in the table, if there is any matching position as a result of acomparison, that position is deleted from the table, the pixel datacorresponding to the positions in the table after the comparing processare extracted from the image data, to create the print data, andcreation of the print data to perform a first dot-forming process isstarted before creation of the tables corresponding to all of thedot-forming processes is finished.
 2. A printing method according toclaim 1, wherein print data for performing a dot-forming process, whichis to be performed after a certain dot-forming process, is created whilethe certain dot-forming process is performed based on the print datacorresponding to the certain dot-forming process.
 3. A printing methodaccording to claim 1, wherein the dot-forming process is a dot-formingprocess for performing upper-end printing for forming the rows of dotsin an upper-end portion of the medium, and wherein the other dot-formingprocess is a dot-forming process for performing normal printing forforming the rows of dots in a central portion of the medium.
 4. Aprinting method according to claim 1, wherein, in a case where, duringthe dot-forming process, a certain nozzle forms dots at specificpositions in the movement direction and, during a different dot- formingprocess performed after the dot-forming process, an other nozzle formsdots to fill in spaces between the dots formed at the specificpositions, information regarding the specific positions in the movementdirection is associated with a position, on the medium in the carryingdirection, of the row of dots to be formed by the certain nozzle and theinformation is stored in the table in association therewith.
 5. Aprinting method according to claim 4, wherein the other nozzle ispositioned at an end in the carrying direction of the plurality ofnozzles.
 6. A printing method according to claim 1, wherein a computerhaving a printer driver installed thereon creates the print data.
 7. Aprinting method according to claim 1, wherein a print control apparatusfor creating the print data and a printing apparatus for forming, on themedium, a plurality of the rows of dots based on the print data areprovided as a single unit.
 8. A printing method comprising: creatingprint data by rearranging an order in which a plurality of pieces ofpixel data which make up image data are arranged; and based on the printdata, alternately repeating a dot-forming process for forming, on amedium, a row of dots along a movement direction by ejecting ink from aplurality of nozzles which move in the movement direction and a carryingprocess for carrying the medium in a carrying direction with respect tothe nozzles, to form, on the medium, a plurality of the rows of dotsarranged in the carrying direction, (A) wherein, every time the printdata for performing a dot-forming process is to be created, positions,on the medium in the carrying direction, of the rows of dots to beformed by the nozzles during that dot-forming process are calculated andstored in a table, and the pixel data corresponding to the positions inthe table are extracted from the image data, to create the print data,(B) wherein print data for performing a dot-forming process, which is tobe performed after a certain dot-forming process, is created while thecertain dot-forming process is performed based on the print datacorresponding to the certain dot-forming process, (C) wherein, whencreating print data for performing a certain dot-forming process, acomparing process is performed in which positions, on the medium in thecarrying direction, of the rows of dots to be formed by the nozzlesduring an other dot-forming process are compared with the positionsstored in the table, if there is any matching position as a result ofthe comparison, that position is deleted from the table, the pixel datacorresponding to the positions in the table after the comparing processare extracted from the image data, to create the print data, andcreation of the print data to perform a first dot-forming process isstarted before creation of the tables corresponding to all of thedot-forming processes is finished, (D) wherein the certain dot-formingprocess is a dot-forming process for performing upper-end printing forforming the rows of dots in an upper-end portion of the medium, andwherein the other dot-forming process is a dot-forming process forperforming normal printing for forming the rows of dots in a centralportion of the medium, (E) wherein, in a case where, during a currentdot-forming process, a certain nozzle forms dots at specific positionsin the movement direction and, during a different dot-forming processperformed after the current dot-forming process, an other nozzle formsdots to fill in spaces between the dots formed at the specificpositions, information regarding the specific positions in the movementdirection is associated with a position, on the medium in the carryingdirection, of the row of dots to be formed by the certain nozzle and theinformation is stored in the table in association therewith, (F) whereinthe other nozzle is positioned at an end in the carrying direction ofthe plurality of nozzles, and (G) wherein a computer having a printerdriver installed thereon creates the print data.
 9. A printing systemcomprising: a print control apparatus for creating print data byrearranging an order in which a plurality of pieces of pixel data whichmake up image data are arranged; and a printing apparatus thatalternately repeats, based on the print data, a dot-forming process forforming, on a medium, a row of dots along a movement direction byejecting ink from a plurality of nozzles which move in the movementdirection and a carrying process for carrying the medium in a carryingdirection with respect to the nozzles, to form, on the medium, aplurality of the rows of dots arranged in the carrying direction,wherein, every time the print data for performing a dot-forming processis to be created, the print control apparatus calculates and stores, ina table, positions, on the medium in the carrying direction, of the rowsof dots to be formed by the nozzles during that dot-forming process,performs a comparing process in which positions, on the medium in thecarrying direction, of the rows of dots to be formed by the nozzlesduring an other dot-forming process are compared with the positionsstored in the table, if there is any matching position as a result of acomparison, deletes that position from the table, extracts, from theimage data, the pixel data corresponding to the positions in the tableafter the comparing process, to create the print data, and startscreation of the print data to perform a first dot-forming process beforecreation of the tables corresponding to all of the dot-forming processesis finished.
 10. A print control apparatus that is installed with aprinter driver program for controlling a printing apparatus, the printerdriver program comprising: a code for creating print data by rearrangingan order in which a plurality of pieces of pixel data which make upimage data are arranged; a code for causing the printing apparatus toalternately repeat, based on the print data, a dot-forming process forforming, on a medium, a row of dots along a movement direction byejecting ink from a plurality of nozzles which move in the movementdirection and a carrying process for carrying the medium in a carryingdirection with respect to the nozzles, to cause the printing apparatusto form, on the medium, a plurality of the rows of dots arranged in thecarrying direction; and a code, utilized every time the print data forperforming a dot-forming process is to be created, for calculating andstoring, in a table, positions, on the medium in the carrying direction,of the rows of dots to be formed by the nozzles during that dot-formingprocess, performing a comparing process in which positions, on themedium in the carrying direction, of the rows of dots to be formed bythe nozzles during an other dot-forming process are compared with thepositions stored in the table, if there is any matching position as aresult of the comparison, deleting that position from the table,extracting, from the image data, the pixel data corresponding to thepositions in the table after the comparing process, to create the printdata, and starting creation of the print data to perform a firstdot-forming process before creation of the tables corresponding to allof the dot-forming processes is finished.